Row hammer refresh command

ABSTRACT

A memory controller issues a targeted refresh command. A specific row of a memory device can be the target of repeated accesses. When the row is accessed repeatedly within a time threshold (also referred to as “hammered” or a “row hammer event”), physically adjacent row (a “victim” row) may experience data corruption. The memory controller receives an indication of a row hammer event, identifies the row associated with the row hammer event, and sends one or more commands to the memory device to cause the memory device to perform a targeted refresh that will refresh the victim row.

PRIORITY

This application is a Continuation of, and claims the benefit ofpriority of, U.S. patent application Ser. No. 13/539,415, filed Jun. 30,2012.

FIELD

Embodiments of the invention are generally related to memory management,and more particularly to sending a refresh command in response to a rowhammer event.

COPYRIGHT NOTICE/PERMISSION

Portions of the disclosure of this patent document may contain materialthat is subject to copyright protection. The copyright owner has noobjection to the reproduction by anyone of the patent document or thepatent disclosure as it appears in the Patent and Trademark Officepatent file or records, but otherwise reserves all copyright rightswhatsoever. The copyright notice applies to all data as described below,and in the accompanying drawings hereto, as well as to any softwaredescribed below: Copyright© 2012, Intel Corporation, All RightsReserved.

BACKGROUND

With advances in computing technology, computing devices are smaller andhave much more processing power. Additionally, they include more andmore storage and memory to meet the needs of the programming andcomputing performed on the devices. The shrinking size of the devicestogether with the increased storage capacity is achieved by providinghigher density devices, where the atomic storage units within a memorydevice have smaller and smaller geometries.

With the latest generation of increased density, intermittent failurehas appeared in some devices. For example, some existing DDR3 basedsystems experience intermittent failures with heavy workloads.Researchers have traced the failures to repeated access to a single rowof memory within the refresh window of the memory cell. For example, fora 32 nm process, if a row is accessed 550K times or more in the 64 msrefresh window, the physically adjacent wordline to the accessed row hasa very high probability of experiencing data corruption. The rowhammering can cause migration across the passgate. The leakage andparasitic currents caused by the repeated access to one row cause datacorruption in a non-accessed physically adjacent row. The failure issuehas been labeled as a ‘row hammer’ or ‘1 row disturb’ issue by the DRAMindustry where it is most frequently seen.

One approach identified to deal with the failure due to row hammer is tolimit the number of accesses allowed per row per refresh cycle, whichhas performance impacts in the system. Another approach identified toaddress the row hammer failure includes decreasing the bottom criticaldimension (BCD) in the buried channel array transistor (BCAT), and/orincreasing channel length to improve the drain induced barrier lowering(DIBL). However, changing the dimension sizes of the devices has bothphysical and practical limitations. To the extent certain dimensions maynow be changed, it would still require changes to the manufacturingprocesses. Also, it leaves open the question of how to address the issuein next-generation products.

Another approach to dealing with the row hammer issue is to decrease thetime between refreshes. However, the refresh time has already been heldconstant even as the density of the devices has increased. Currentdevices are required to perform refresh on larger and larger areas inthe same period of time. Thus, further decreasing the refresh time wouldcause a performance impact in the system, such as by requiringadditional refresh overhead in the memory devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description includes discussion of figures havingillustrations given by way of example of implementations of embodimentsof the invention. The drawings should be understood by way of example,and not by way of limitation. As used herein, references to one or more“embodiments” are to be understood as describing a particular feature,structure, or characteristic included in at least one implementation ofthe invention. Thus, phrases such as “in one embodiment” or “in analternate embodiment” appearing herein describe various embodiments andimplementations of the invention, and do not necessarily all refer tothe same embodiment. However, they are also not necessarily mutuallyexclusive.

FIG. 1 is a block diagram of an embodiment of a system that provides atargeted refresh command.

FIG. 2A is a block diagram of an embodiment of a system that provides atargeted refresh for a victim row of a memory array.

FIG. 2B is a block diagram of an embodiment of a system that provides atargeted refresh for a victim row of a memory array, where the victimrow is in a region different from the target of excessive access.

FIG. 3 is a block diagram of an embodiment of a system that uses N pinsto indicate an address of a targeted refresh command.

FIG. 4 is an embodiment of a command truth table supporting a targetedrefresh command.

FIG. 5 is a timing diagram of an embodiment of signaling thatillustrates timing for a targeted refresh command.

FIG. 6 is a flow diagram of an embodiment of a process for targetedrefresh of a victim row of a memory device.

FIG. 7 is a block diagram of an embodiment of a computing system inwhich targeted refresh can be implemented.

FIG. 8 is a block diagram of an embodiment of a mobile device in whichtargeted refresh can be implemented.

Descriptions of certain details and implementations follow, including adescription of the figures, which may depict some or all of theembodiments described below, as well as discussing other potentialembodiments or implementations of the inventive concepts presentedherein.

DETAILED DESCRIPTION

As described herein, a memory controller sends a targeted refreshcommand to a memory device to address a row hammer condition or rowhammer event. When a specific row of a memory device is repeatedlyaccessed within a certain time window, a physically adjacent row mayexperience data corruption. The repeated access within the time windowis referred to herein as a row hammer event or row hammer condition. Thephysically adjacent row is a victim row to the row hammer event. Asdescribed herein the memory controller receives an indication of a rowhammer event, in which a specific row is accessed more than a thresholdnumber of times within the time window. The memory controller identifiesthe row associated with the row hammer event, and sends one or morecommands to the memory device to cause the memory device to perform atargeted refresh that will refresh the victim row or rows.

The theoretical maximum number of times a row can be accessed within a64 ms window (e.g., a refresh window) is 1.35 million times (64 msrefresh window divided by 47 ns access time) for current DRAMs (dynamicrandom access memory). The practical maximum without risking datacorruption in the victim rows is much lower, and depends on the processtechnology used. However, by detecting a row hammer event and sending atargeted refresh command, the risk of data corruption can be reducedwithout restricting access to a specific row of memory.

The examples provided herein primarily discuss the row hammer issue withrespect to DRAM. However, it will be understood that the row hammerissue is more generally a memory device scaling issue, which occurs asmemory densities increase. Thus, the descriptions with respect to DRAMwill be understood as non-limiting examples that can be applied to othermemory technologies that include memory controller or equivalent logic.The targeted refresh command described herein is compatible with any ofa number of memory technologies, such as DDR4 (dual data rate version 4,specification in development as of the filing of this application),LPDDR4 (low power dual data rate version 4, specification in developmentas of the filing of this application), or WIDEIO (specification indevelopment as of the filing of this application).

In a memory device, rows that are physically adjacent can often belogically labeled differently from one manufacturer to another.Typically a manufacturer maps logically adjacent rows of memory by aphysical address offset, and the offsets can be different amongdifferent manufacturers. The memory device itself is configured todetermine how to map access requests to the physical memory resources.Memory controllers are generally designed to be compatible with manydifferent types of memory devices, and so they are generally notdesigned specifically with respect to any particular manufacturer'sdevice. Thus, memory controllers do not traditionally have logic orinformation to indicate what rows are physically adjacent.

In one embodiment, the memory controller sends information indicatingwhat row is getting hammered by access requests in conjunction withsending the targeted refresh command to cause the memory device torefresh the correct victim row or rows. Thus, the memory controller neednot directly indicate the row(s) to be refreshed, but instead simplyidentify the row getting hammered. The memory device itself cancalculate what victim row or rows will be affected by the row hammerevent based on the memory layout used by the memory device. In a typicalrefresh scenario, the memory device itself tracks what needs to berefreshed when. The memory device refreshes the victim row(s) by openingthe row and then closing the row(s) to refresh.

It will be understood that for the memory controller to indicate anaddress of the hammered row to cause the memory device to refresh victimrow(s) of the hammered row requires a certain number of bits to identifya specific address. In one embodiment, the memory controller identifiesa specific address. In another embodiment, the memory controlleridentifies an area larger than a specific row. Thus, a memory controllercan identify a specific block, a specific row, or an area, depending onthe chosen configuration. The cost of identifying a very specificaddress is the number of bits required. The cost of identifying theaddress more generally is that the memory device needs to refresh alarger area, making the memory device unavailable for a longer refreshtime.

In one embodiment, the memory controller indicates address informationby sending address information to the memory device. In one embodiment,one or more additional pins or lines can be added between the memorycontroller and the memory device embeds address information into anexisting command to identify address information. Thus, the targetedrefresh command can be a modified existing command and/or a modifiedexisting command in conjunction with the use of one or more additionalpins or lines. In one embodiment, the targeted refresh command includessending a command and address multiple times (e.g., three times). In oneembodiment, the address can be modified in the successive commands(e.g., sending the address+1 and then the address−1 in two successivecommands). Other embodiments are possible. In one embodiment, the memorycontroller sends a targeted refresh command, which the memory deviceseparates into one or more groups of Activate and Precharge commands.

It is common for a memory controller to issue a refresh command to causea memory device to perform a refresh in accordance with refresh trackingperformed by the memory device. Thus, the memory controller need onlyprovide the command, and the memory device can determine how and what torefresh. In one embodiment, the memory controller issues a targetedrefresh command including sending an Activate command with addressinformation. In one embodiment, the memory controller issues a targetedrefresh command including sending a Refresh command with addressinformation. It will be understood that other existing commands could be“doubled up” with address information to trigger a targeted refresh.Additionally, a completely new command can be used as a command totrigger or cause a targeted refresh.

FIG. 1 is a block diagram of an embodiment of a system that provides atargeted refresh command. System 100 includes memory device 110 coupledto memory controller 120. Memory device 110 can include any type ofmemory technology that has adjacent rows of memory cells, where data isaccessible via a wordline or the equivalent. In one embodiment, memorydevice 110 includes dynamic random access memory (DRAM) technology.

Memory device 110 includes target row 112, which is the row of memorysubject to hammering, or being accessed repeatedly within a given timeperiod. The target row is the target of the row hammer event. In manymodern memory devices, the architecture of the semiconductor layoutcauses one or more physically adjacent rows to be at risk of becomingcorrupted. The rows at risk of becoming corrupted due to row hammer oftarget row 112 are illustrated as victim row 114 and victim row 116.Either or both of victim rows 114, 116 can be at risk, depending on thephysical layout of memory device 110.

It will be understood that different memory device manufacturers usedifferent logic and architectures to utilize the memory resources of thedevices. For example, different memory device manufacturers can usedifferent offsets to map between logical memory addresses used in thehost processor (not shown) and the physical memory addresses usedinternally to memory device 110. In one embodiment, memory controller120 utilizes the same logical memory addresses as used by the hostprocessor. Thus, in one embodiment, memory controller 120 provides a rowaddress to memory device 110 indicating target row 112. The memorycontroller can indicate the row address in conjunction with and/or aspart of a command that it issues to memory device 110. The memory devicecan then compute the specific address or addresses of victim row(s) 114,116. Memory device 110 then performs a targeted refresh on the adjacent,victim row.

Memory controller 120 generates targeted refresh command 122 to causethe memory controller to perform a targeted refresh in response todetecting a row hammer event. In one embodiment, targeted refreshcommand 122 includes a series of commands. The commands can all be thesame commands, or a different combination of commands can be sent. Forexample, in one embodiment, each targeted refresh command (whether a newcommand, or a doubled-up command) can be followed by a Prechargecommand. In one embodiment, the memory controller sends a sequence ofmultiple commands with address and Precharge commands to cause thetargeted refresh in the memory device. In one embodiment, the sequenceis three groups of command+address followed by a Precharge command(e.g., Cmd+Addr, Pre, Cmd+Addr, Pre, Cmd+Addr, Pre). In one embodiment,the memory device (e.g., a DRAM) generates the targeted refresh commands(such as Activate commands) and Precharge commands in response to atargeted refresh command issued by the memory controller indicating anaddress. The address can be kept the same for each command in theseries, especially if the address is specified for an area instead of aspecific row. In an alternative embodiment, the address can be variedfor each command, such as sending Addr, Addr+1, and Addr−1 for the threecommands. The order of the addresses could be altered in any way (e.g.,Addr−1, Addr, Addr+1. or Addr, Addr−1, Addr+1, or some othercombination).

Detector 130 represents hardware and/or software or other logic thatenables system 100 to detect a row hammer event. The mechanism ormechanisms used to detect the row hammer condition are beyond the scopeof the discussion herein, and will not be discussed in detail. Theprimary point is that the detector 130 can determine when target row 112experiences repeated accesses within a threshold. Detector 130 caninclude hardware and/or logic at memory device 110, memory controller120, and/or separate from either the memory device or the memorycontroller.

The mechanisms include some way of determining a number of times a rowis accessed, as well as determining the period of time in which theaccesses occur. The row hammer event is not simply about how many timesa row is accessed, but how many times in a given time period. Once a rowis refreshed, the conditions that could cause data corruption areovercome. Thus, the time period for the monitoring should be based atleast in part on the refresh rate. Targeted refresh command 122 canovercome the conditions that cause data corruption in between thenormally scheduled refresh event that occurs periodically on the refreshcycle.

In one embodiment, the issuing of command 122 is done at least partiallyin conjunction with setting a value in Mode Register 118. Mode Register118 is a register, or table, or other mechanism used to storeconfiguration information for memory device 110. The configurationinformation can vary from one implementation to another, but differentsettings of the Mode Register can change how a given command sent on acommand bus (e.g., a command/address (C/A) bus) is interpreted by memorydevice 110. In one embodiment, targeted refresh command 122 is sent onthe C/A bus together with setting a value in the Mode Register totrigger the memory device to interpret certain bits of the command asaddress bits.

It will be understood that there can be a number of different ways toprovide row address information from memory controller 120 to memorydevice 110. One option is to use the Mode Register as discussed above. Acommand can be reused with a different Mode Register state set to havethe memory device interpret the same command a different way, andspecifically, to trigger a targeted refresh. Such an approach can bereferred to as multiplexing the signal lines, by providing differentinformation with the same bits, depending on the Mode Register state.

Two examples of commands that could be reused in a DRAM-device contextare the Activate and the Refresh commands, which both include addressinformation in the commands. As discussed above, the address informationcan be provided specifically, or more generally. For a more generalindication of the address, the number of bits used would not besufficient to provide a specific address for the hammered row. Thus, theaddress information can be interpreted as being truncated by a certainbit offset, and memory device 110 would refresh a larger area. Thetruncation can be a function of memory device density.

FIG. 2A is a block diagram of an embodiment of a system that provides atargeted refresh for a victim row of a memory array, such as a DRAMarray. FIG. 2B is a block diagram of an embodiment of a system thatprovides a targeted refresh for a victim row of a memory array, such asa DRAM array, where the victim row is in an area of memory differentfrom the target of excessive access. System 200 includes DRAM 210 orother memory device, and memory controller 230 coupled to the memorydevice. System 200 provides one example of a system in accordance withsystem 100 of FIG. 1.

DRAM 210 includes memory rows 212, which are rows of memory inaccordance with known memory architectures or their derivatives.Briefly, a row of memory includes one or more addressable columns ofmemory cells, as identified by a column address strobe or signal (CAS).The rows are addressable via a row address strobe or signal (RAS).Address map 220 includes logic to map address information from memorycontroller 230 to physical memory locations in DRAM 210. It isunderstood that memory is typically accessed in such a way that“adjacent” memory addresses provided by memory controller 230 do notnecessarily map to physically adjacent memory locations in DRAM 210.Rather, each adjacent memory address as provided by memory controller230 maps to addresses that are located as some consistent offset. Forexample, addresses 0xX0h, 0xX1h, and 0xX2h could be located at physicallocations 0xY0h, 0xY3h, and 0xY7h, respectively, where the offset is‘4’. In the example, ‘X’ represents the higher bit information of theaddresses as provided by the memory controller, and ‘Y’ represents thehigher bit information of the addresses as mapped within DRAM 210. Thus,the memory device itself can determine the victim row based on theconfiguration of the device in conjunction with the address informationprovided by the memory controller with a targeted refresh command.

Referring specifically to the figures, FIG. 2A illustrates target row214 and adjacent victim row 216, where both the target row and thevictim row are in the same area of memory 242. FIG. 2B illustratestarget row 254 in area 244, and victim row 256 in area 246. Target rows214 and 254 are the targets of row hammer conditions to which memorycontroller 230 responds by sending targeted refresh commands. Victimrows 216 and 256 represent the rows that need to be refreshed inresponse to the row hammer condition.

As illustrated, the victim row can be located in the same region ofmemory (FIG. 2A), but is not necessarily located in the same region ofmemory (FIG. 2B). The region of memory can be understood as a logicaland/or physical separation of memory. In one embodiment, a row of memoryin a different memory bank can become the victim of the row hammerevent. Address map 220 enables DRAM 210 to identify what row to refreshin response to the targeted refresh command.

In one embodiment, memory controller 230 identifies a specific addressfor the target row. The specific address can be a specific physicaladdress. In one embodiment, the memory controller identifies a specificvirtual memory address of the target row (e.g., rows 214 and 254). Inone embodiment, memory controller 230 only identifies a regionassociated with the hammered row. The region can be more specific thanthe specificity of areas 242, 244, and 246. Thus, reference to targetinga refresh to an area or a region can be to any size grouping of rows.The grouping is not necessarily restricted by the virtual layout of thememory device. The grouping can be referred to as a region to berefreshed.

Thus, the memory controller can identify a region associated with a rowhammer event, and in response to the command, the memory devicerefreshes the region or another region associated with a victim row ofthe hammered row. The refresh region is not necessarily the same regionidentified by the memory controller, but could be an adjacent region ifthe memory device determines that the victim row is in the adjacentregion. The memory controller can identify a region associated with thehammered row to reduce the number of pins or signal lines needed tospecify the address of the hammered row. The consequence of using lessspecificity in identifying the hammered row is the need to refresh alarger region or area to make sure to refresh the victim, since thevictim cannot be specified with exactness in such cases.

FIG. 3 is a block diagram of an embodiment of a system that uses N pinsto indicate an address of a targeted refresh command. System 300 is asystem that includes a memory device coupled to a host processor via amemory controller, and can be one example of a system in accordance withsystem 100 of FIG. 1. System 300 includes memory device DRAM 310 coupledto memory controller 320. Memory controller 320 is coupled in turn tohost processor 340.

Host processor 340 can be any type of processing unit, processor, ormicrocontroller. Host processor 340 performs the primary execution ofoperations in system 300. Operations executed by host processor 340typically originate from instructions and data stored in DRAM 310. DRAM310 is a memory device in accordance with any embodiment describedherein. DRAM 310 includes memory cells 314, which stores the data andinstructions used by host processor 340. In one embodiment, DRAM 310 isa volatile memory, or a memory device whose contents arenon-deterministic if power is interrupted to the device. Thus, avolatile memory requires a regular power source to allow it to refreshthe memory cells to keep the data from become lost or corrupted.

DRAM 310 includes pins 312, which interface with pins 322 of memorycontroller 320. Memory access from host processor 340 typically goesthrough memory controller 320. In one embodiment, memory controller 320is part of host processor 340. In an alternate embodiment, memorycontroller is part of a supporting “chipset” or hardware logic thatprovides an infrastructure for power and interface logic for a hardwareplatform of which host processor 340 is a part. In one embodiment, pins322 include pin or pins 324, which can be used to provide addressinformation in conjunction with a targeted refresh command. As discussedabove, the targeted refresh command can be a command sequence ofmultiple commands in series that trigger the targeted refresh in thememory device, such as DRAM 310. In an alternate embodiment, the memorycontroller can send a single command, and the memory device can thengenerate commands to refresh or activate the victim row(s), and commandsto precharge the victim row(s). Other pins (not shown) could also beused in sending the targeted refresh command to DRAM 310. In oneembodiment, pins 324 include more than a single pin. Thus, theinterconnection line is labeled as have a width “N”, where N is aninteger>0.

As previously mentioned, the specificity of the address information canbe lower or higher depending on the system configuration. In oneembodiment, the system is configured to use a Bank Activate command,which has four pins or lines specified for sending address information.In one embodiment where a Bank Activate command is reused as a targetedrefresh command, the system is configured with another pin or line, anActivate Enable pin, as well as three additional pins or lines forspecifying address information. Depending on how N is interpreted, N inthis configuration could be considered to be 8 (4 original address pins,3 additional address pins, and Activate Enable). In the same scenario, Ncould be interpreted as being only 3 to represent the additional addressinformation pins. N could also be interpreted as some other number inthis configuration.

Without specifying additional address information, the targeted refreshcommand would not include 3 LSBs (least significant bits) worth ofinformation, and the memory device (e.g., DRAM 310) would have to cyclemore area per targeted refresh command. Thus, additional addressinformation can be specified if additional pins are used; otherwise, theaddress associated with the targeted refresh command is less specific.

As mentioned above, detector 330 enables memory controller 320 toidentify a row hammer condition to be able to respond to the row hammercondition with a targeted refresh command. Detector 330 is illustratedas being part of memory controller 320. In one embodiment, themechanisms that perform the actual detection reside in DRAM 310. In analternate embodiment, detector 330 resides at least partly outside ofmemory controller 320 or DRAM 310, such as being part of the hardwareplatform of system 300.

DRAM 310 includes victim logic 316, which represents logic to determinewhat row or rows are at risk of corruption due to the row hammercondition. In one embodiment, victim logic 316 can be at least partiallyexecuted at memory controller 320. However, for the sake of broaderinteroperability between memory controller 320 and other types of memorydevices, victim logic 316 generally resides at DRAM 310. Thus, memorycontroller 320 need only identify the fact that a row hammer conditionexists, and then send a command specifying the address or address rangeof the target row. DRAM 310 can then use a map or other logic todetermine what row or rows are potential victims.

DRAM 310 includes control logic 318, which includes logic to performrefresh of memory 314. Each memory device includes some logic to keeptrack of what memory cells have been refreshed, and what rows are nextdue for a refresh. Control logic 318 can implement the actual targetedrefresh based on receiving a targeted refresh command from memorycontroller 320.

FIG. 4 is an embodiment of a command truth table supporting a targetedrefresh command. Command truth table 400 represents one example of atruth table for a memory device. More specifically, table 400 representsa working draft of a specification for DDR4 memory. The column to theleft identifies supported functions. The columns to the right identifythe value of different signals to specify the identified functions.

Of particular note in table 400 for purposes of discussion here iscommand 430, which is Row Hammer. It will be observed that theillustrated embodiment of Row Hammer is identical to Bank Activate (thecommand above it), with the exception of the value of signal 410, ACT_n.In one embodiment, ACT_n is a pin not in previous memory standards. Thesignal on ACT_n indicates whether or not the command is Row Hammer orBank Activate. It is shown as active-low, but could alternatively beconfigured to be active-high. Both commands can identify an address, asindicated by the row address bits.

It will be observed that the three columns labeled as 420 include RAS,CAS and WE signals. However, these commands can be controlled internallyby the memory device itself. Thus, by multiplexing these signals withadditional address information (address bits A16, A15, and A14,respectively), enables more address information to be provided to moreparticularly identify the address of the target of the row hammercondition.

When ACT is set (e.g., column 410), the memory device reads RAS/CAS/WEas row address information. When ACT is not set, the memory device readsRAS/CAS/WE as traditional memory access encoding. As mentioned above,the address information could be identified for block, specific row, orsome other size area. The refresh can be as specific or as wide asdesired for the system.

While the Activate command is shown as being doubled up by the use ofsignal ACT_n, Refresh or any other command could be used. Alternatively,a completely new command could be used for targeted refresh. Asillustrated, the targeted refresh command can be said to be embedded inan Activate command. The memory device identifies the victim row basedon the address inside command 430.

In one embodiment, prior to setting command 430 on a C/A bus to thememory device, the memory controller places the memory device in a ‘rowhammer mode’ via a Mode Register bit or bits. In one embodiment, thememory controller provides row address along with bank group and bankaddress to the memory device. The memory device performs a targetedrefresh using the address provided to the physical row adjacent to theaddress. After allowing a period of time for the refresh command tooccur (see FIG. 5 below), the memory controller can then remove thememory device from ‘row hammer mode’ by resetting the MR bit.

FIG. 5 is a timing diagram of an embodiment of signaling thatillustrates timing for a targeted refresh command. Clock signal CLK 510illustrates clock cycles in a system that allows a targeted refreshcommand. MR 520 represents the timing of a specific Mode Register state.In the case of a targeted refresh command, in one embodiment, a specificrefresh or targeted refresh state exists with respect to the ModeRegister by setting one or more bits of the Mode Register. In anembodiment where a Mode Register state is used, the Mode Register stateis set prior to the targeted refresh command being sent. As illustrated,the Mode Register state MR 520 is enabled on a falling edge, but couldalternatively be enabled on a rising edge.

The signal illustrated as “Ready 540” represents a memory device readyindicator. Ready signal 540 indicates a period of time in which thememory device is inaccessible following a targeted refresh command.Command line 530 illustrates a command “RF+ADDR,” which represents atargeted refresh command. The portion ‘RF’ represents the command forthe receiving memory device to perform a refresh. The ‘ADDR’ portionrepresents the address indicated to the memory device, which causes thememory device to refresh a specific victim row, or a region with avictim row based on the address.

It will be understood that command line 530 can include multiplecommands sent in sequence to generate a targeted refresh, and/or asingle command can be separated into multiple commands at the memorydevice. All commands can be sent or generated while the Mode Registerstate is active (e.g., set the Mode Register state, send a series ofcommands, and then reset the Mode Register state). The commands can besent or generated all together, in which case the memory device canbuffer the commands and execute them in the order received, or thememory controller can wait the time tRF to allow the memory device torefresh prior to sending the next command. If the commands are sent orgenerated in a sequence, the memory device will become unavailable forsome time period that could be multiples of tRF. The memory controllertypically will not send a command during the refresh time. However, inan embodiment where the memory controller issues multiple commands totrigger the targeted refresh, the memory device and the memorycontroller can be configured to enable an exception to allow a series ofcommand based on the triggering of the Mode Register state shown in line520.

For some period of time tRF after the issuance of the targeted refreshcommand, the memory device will be inaccessible, as seen by the troughin Ready 540. It will be understood that the time period tRF is shorterthan a refresh cycle time tRFC, or a time period during which the memorydevice is unavailable following a generic refresh command. The typicaltRFC is somewhere around 300-400 nanoseconds. However, the time for tRFcan be an order of magnitude smaller than tRFC. Thus, tRF associatedwith a targeted refresh command is very low compared to the tRFCassociated with a standard refresh command. The inaccessibility of thememory device refers to the fact that there are no additional commandssent during the blocked-out time period while a refresh is taking place(rRFC for a full refresh, tRF for a targeted refresh).

FIG. 6 is a flow diagram of an embodiment of a process for targetedrefresh of a victim row of a memory device. The memory controllerreceives a row hammer indication from a row hammer monitor, 602. The rowhammer monitor includes any mechanism used to track and indicate that aspecific row has been accessed more than a threshold number of timeswithin a given time period. The threshold number can be pre-configuredin the system, and/or the threshold can be configurable. The time periodis the time period between refreshes, seeing that if the victim row isrefreshed, the row hammer condition will be cured.

The monitor can identify a specific row of memory associated with therow hammer indication, 604. The memory controller determines to issue atargeted refresh command to alleviate the row hammer condition. In oneembodiment, the memory controller sets a Mode Register to enable atargeted refresh command, 606. In one embodiment, a targeted refreshcommand can be issued without setting the Mode Register.

The memory controller sends one or more commands to the memory device tocause the memory device to perform a targeted refresh on the victimrow(s) of the identified address, 608. In one embodiment, the memorydevice generates multiple commands in response to one or more commandssent by the memory controller. The memory controller can send theaddress information separately, or as part of the targeted refreshcommand. In one embodiment, the memory device itself identifies thevictim row or region associated with the identified address, 610. Thememory device then performs the targeted refresh on the victim row orregion responsive to the command, 612. The memory controller can thenreset the Mode Register to disable the targeted refresh, 614.

FIG. 7 is a block diagram of an embodiment of a computing system inwhich targeted refresh can be implemented. System 700 represents acomputing device in accordance with any embodiment described herein, andcan be a laptop computer, a desktop computer, a server, a gaming orentertainment control system, a scanner, copier, printer, or otherelectronic device. System 700 includes processor 720, which providesprocessing, operation management, and execution of instructions forsystem 700. Processor 720 can include any type of microprocessor,central processing unit (CPU), processing core, or other processinghardware to provide processing for system 700. Processor 720 controlsthe overall operation of system 700, and can be or include, one or moreprogrammable general-purpose or special-purpose microprocessors, digitalsignal processors (DSPs), programmable controllers, application specificintegrated circuits (ASICs), programmable logic devices (PLDs), or thelike, or a combination of such devices.

Memory subsystem 730 represents the main memory of system 700, andprovides temporary storage for code to be executed by processor 720, ordata values to be used in executing a routine. Memory subsystem 730 caninclude one or more memory devices such as read-only memory (ROM), flashmemory, one or more varieties of random access memory (RAM), or othermemory devices, or a combination of such devices. Memory subsystem 730stores and hosts, among other things, operating system (OS) 736 toprovide a software platform for execution of instructions in system 700.Additionally, other instructions 738 are stored and executed from memorysubsystem 730 to provide the logic and the processing of system 700. OS736 and instructions 738 are executed by processor 720.

Memory subsystem 730 includes memory device 732 where it stores data,instructions, programs, or other items. In one embodiment, memorysubsystem includes memory controller 734, which is a memory controllerin accordance with any embodiment described herein, and which provides atargeted refresh command to memory device 732 based on a row hammercondition. The targeted refresh command causes memory device 732 toperform a targeted refresh, which is a refresh operation off-cycle,meaning it is not on the regularly scheduled cycle of refreshes, and isnot necessarily on an area tracked by the memory device as the next areato refresh. Rather, the region refreshed is based on a victim row orregion identified based on an address associated with the targetedrefresh command(s).

Processor 720 and memory subsystem 730 are coupled to bus/bus system710. Bus 710 is an abstraction that represents any one or more separatephysical buses, communication lines/interfaces, and/or point-to-pointconnections, connected by appropriate bridges, adapters, and/orcontrollers. Therefore, bus 710 can include, for example, one or more ofa system bus, a Peripheral Component Interconnect (PCI) bus, aHyperTransport or industry standard architecture (ISA) bus, a smallcomputer system interface (SCSI) bus, a universal serial bus (USB), oran Institute of Electrical and Electronics Engineers (IEEE) standard1394 bus (commonly referred to as “Firewire”). The buses of bus 710 canalso correspond to interfaces in network interface 750.

System 700 also includes one or more input/output (I/O) interface(s)740, network interface 750, one or more internal mass storage device(s)760, and peripheral interface 770 coupled to bus 710. I/O interface 740can include one or more interface components through which a userinteracts with system 700 (e.g., video, audio, and/or alphanumericinterfacing). Network interface 750 provides system 700 the ability tocommunicate with remote devices (e.g., servers, other computing devices)over one or more networks. Network interface 750 can include an Ethernetadapter, wireless interconnection components, USB (universal serialbus), or other wired or wireless standards-based or proprietaryinterfaces.

Storage 760 can be or include any conventional medium for storing largeamounts of data in a nonvolatile manner, such as one or more magnetic,solid state, or optical based disks, or a combination. Storage 760 holdscode or instructions and data 762 in a persistent state (i.e., the valueis retained despite interruption of power to system 700). Storage 760can be generically considered to be a “memory,” although memory 730 isthe executing or operating memory to provide instructions to processor720. Whereas storage 760 is nonvolatile, memory 730 can include volatilememory (i.e., the value or state of the data is indeterminate if poweris interrupted to system 700).

Peripheral interface 770 can include any hardware interface notspecifically mentioned above. Peripherals refer generally to devicesthat connect dependently to system 700. A dependent connection is onewhere system 700 provides the software and/or hardware platform on whichoperation executes, and with which a user interacts.

FIG. 8 is a block diagram of an embodiment of a mobile device in whichtargeted refresh can be implemented. Device 800 represents a mobilecomputing device, such as a computing tablet, a mobile phone orsmartphone, a wireless-enabled e-reader, or other mobile device. It willbe understood that certain of the components are shown generally, andnot all components of such a device are shown in device 800.

Device 800 includes processor 810, which performs the primary processingoperations of device 800. Processor 810 can include one or more physicaldevices, such as microprocessors, application processors,microcontrollers, programmable logic devices, or other processing means.In one embodiment, processor 810 includes optical interface componentsin addition to a processor die. Thus, the processor die and photoniccomponents are in the same package. Such a processor package caninterface optically with an optical connector in accordance with anyembodiment described herein.

The processing operations performed by processor 810 include theexecution of an operating platform or operating system on whichapplications and/or device functions are executed. The processingoperations include operations related to I/O (input/output) with a humanuser or with other devices, operations related to power management,and/or operations related to connecting device 800 to another device.The processing operations can also include operations related to audioI/O and/or display I/O.

In one embodiment, device 800 includes audio subsystem 820, whichrepresents hardware (e.g., audio hardware and audio circuits) andsoftware (e.g., drivers, codecs) components associated with providingaudio functions to the computing device. Audio functions can includespeaker and/or headphone output, as well as microphone input. Devicesfor such functions can be integrated into device 800, or connected todevice 800. In one embodiment, a user interacts with device 800 byproviding audio commands that are received and processed by processor810.

Display subsystem 830 represents hardware (e.g., display devices) andsoftware (e.g., drivers) components that provide a visual and/or tactiledisplay for a user to interact with the computing device. Displaysubsystem 830 includes display interface 832, which includes theparticular screen or hardware device used to provide a display to auser. In one embodiment, display interface 832 includes logic separatefrom processor 810 to perform at least some processing related to thedisplay. In one embodiment, display subsystem 830 includes a touchscreendevice that provides both output and input to a user.

I/O controller 840 represents hardware devices and software componentsrelated to interaction with a user. I/O controller 840 can operate tomanage hardware that is part of audio subsystem 820 and/or displaysubsystem 830. Additionally, I/O controller 840 illustrates a connectionpoint for additional devices that connect to device 800 through which auser might interact with the system. For example, devices that can beattached to device 800 might include microphone devices, speaker orstereo systems, video systems or other display device, keyboard orkeypad devices, or other I/O devices for use with specific applicationssuch as card readers or other devices.

As mentioned above, I/O controller 840 can interact with audio subsystem820 and/or display subsystem 830. For example, input through amicrophone or other audio device can provide input or commands for oneor more applications or functions of device 800. Additionally, audiooutput can be provided instead of or in addition to display output. Inanother example, if display subsystem includes a touchscreen, thedisplay device also acts as an input device, which can be at leastpartially managed by I/O controller 840. There can also be additionalbuttons or switches on device 800 to provide I/O functions managed byI/O controller 840.

In one embodiment, I/O controller 840 manages devices such asaccelerometers, cameras, light sensors or other environmental sensors,gyroscopes, global positioning system (GPS), or other hardware that canbe included in device 800. The input can be part of direct userinteraction, as well as providing environmental input to the system toinfluence its operations (such as filtering for noise, adjustingdisplays for brightness detection, applying a flash for a camera, orother features).

In one embodiment, device 800 includes power management 850 that managesbattery power usage, charging of the battery, and features related topower saving operation. Memory subsystem 860 includes memory device(s)862 for storing information in device 800. Memory subsystem 860 caninclude nonvolatile (state does not change if power to the memory deviceis interrupted) and/or volatile (state is indeterminate if power to thememory device is interrupted) memory devices. Memory 860 can storeapplication data, user data, music, photos, documents, or other data, aswell as system data (whether long-term or temporary) related to theexecution of the applications and functions of system 800.

In one embodiment, memory subsystem 860 includes memory controller 864(which could also be considered part of the control of system 800, andcould potentially be considered part of processor 810). Memorycontroller 864 issues a targeted refresh command based on a row hammercondition at a specific row of memory of memory device 862.

Connectivity 870 includes hardware devices (e.g., wireless and/or wiredconnectors and communication hardware) and software components (e.g.,drivers, protocol stacks) to enable device 800 to communicate withexternal devices. The device could be separate devices, such as othercomputing devices, wireless access points or base stations, as well asperipherals such as headsets, printers, or other devices.

Connectivity 870 can include multiple different types of connectivity.To generalize, device 800 is illustrated with cellular connectivity 872and wireless connectivity 874. Cellular connectivity 872 refersgenerally to cellular network connectivity provided by wirelesscarriers, such as provided via GSM (global system for mobilecommunications) or variations or derivatives, CDMA (code divisionmultiple access) or variations or derivatives, TDM (time divisionmultiplexing) or variations or derivatives, LTE (long termevolution—also referred to as “4G”), or other cellular servicestandards. Wireless connectivity 874 refers to wireless connectivitythat is not cellular, and can include personal area networks (such asBluetooth), local area networks (such as WiFi), and/or wide areanetworks (such as WiMax), or other wireless communication. Wirelesscommunication refers to transfer of data through the use of modulatedelectromagnetic radiation through a non-solid medium. Wiredcommunication occurs through a solid communication medium.

Peripheral connections 880 include hardware interfaces and connectors,as well as software components (e.g., drivers, protocol stacks) to makeperipheral connections. It will be understood that device 800 could bothbe a peripheral device (“to” 882) to other computing devices, as well ashave peripheral devices (“from” 884) connected to it. Device 800commonly has a “docking” connector to connect to other computing devicesfor purposes such as managing (e.g., downloading and/or uploading,changing, synchronizing) content on device 800. Additionally, a dockingconnector can allow device 800 to connect to certain peripherals thatallow device 800 to control content output, for example, to audiovisualor other systems.

In addition to a proprietary docking connector or other proprietaryconnection hardware, device 800 can make peripheral connections 880 viacommon or standards-based connectors. Common types can include aUniversal Serial Bus (USB) connector (which can include any of a numberof different hardware interfaces), DisplayPort including MiniDisplayPort(MDP), High Definition Multimedia Interface (HDMI), Firewire, or othertype.

In one aspect, a memory subsystem includes hardware connectors to coupleto a memory device having multiple rows of memory and a memorycontroller coupled to the hardware connectors. The memory controller isto receive an indication via the hardware connectors that repeatedaccess to a specific row of the memory device exceeds a threshold,identify an address of the specific row, and send a command to thememory device to perform a targeted refresh, the command to cause thememory device to perform a refresh targeted to a victim row physicallyadjacent to the identified row.

In one embodiment, the memory controller is to identify the address byidentifying a specific physical address for the specific row. In oneembodiment, the memory controller is to identify the address byidentifying a virtual address of the specific row that the memory devicemaps to a physical address of the physically adjacent row. In oneembodiment, the memory controller is to identify the address byidentifying an address of the specific row associated with theindication of repeated access, wherein the memory device identifies thephysically adjacent row based on the address of the specific rowassociated with the indication of repeated memory access and aconfiguration of the memory device.

In one embodiment, the memory controller is to identify the address byidentifying a region of memory that includes the specific row, whereinthe memory device refreshes the identified region, including thephysically adjacent row. In one embodiment, the memory controller is toidentify the address by identifying the address inside the command. Inone embodiment, the command is embedded in an activation command for thememory device. In one embodiment, the memory controller further is toset a value in a Mode Register in conjunction with sending the command.

In one embodiment, the memory controller is to send a sequence ofcommands to cause the memory device to perform the targeted refresh. Inone embodiment, the memory controller is to send an activate refreshcommand followed by a precharge command. In one embodiment, the memorycontroller is to send a targeted refresh command multiple times insequence. In one embodiment, the memory controller is to send adifferent address with each of the targeted refresh commands in thesequence. In one embodiment, the memory device is to generate a sequenceof commands in response to the targeted refresh command from the memorycontroller.

In one aspect, an electronic device includes a memory subsystem having amemory device to store data and a memory controller coupled to thememory device. The memory device includes multiple rows of memory. Thememory controller is to receive an indication from the memory devicethat repeated access to a specific row of the memory device exceeds athreshold, identify an address of the specific row, and send a commandto the memory device to perform a targeted refresh. The command from thememory controller is to cause the memory device to perform a refreshtargeted to a victim row physically adjacent to the identified row. Theelectronic device further includes a multicore processor coupled to thememory subsystem to access the memory subsystem during execution of theprocessor.

In one embodiment, the memory device comprises a dynamic random accessmemory (DRAM) device. In one embodiment, the memory controller is toidentify the address by identifying a specific physical address for thespecific row. In one embodiment, the memory controller is to identifythe address by identifying a virtual address of the specific row thatthe memory device maps to a physical address of the physically adjacentrow. In one embodiment, the memory controller is to identify the addressby identifying an address of the specific row associated with theindication of repeated access, wherein the memory device identifies thephysically adjacent row based on the address of the specific rowassociated with the indication of repeated memory access and aconfiguration of the memory device.

In one embodiment, the memory controller is to identify the address byidentifying a region of memory that includes the specific row, whereinthe memory device refreshes the identified region, including thephysically adjacent row. In one embodiment, the memory controller is toidentify the address by identifying the address inside the command. Inone embodiment, the command is embedded in an activation command for thememory device. In one embodiment, the memory controller further is toset a value in a Mode Register in conjunction with sending the command.

In one embodiment, the memory controller is to send a sequence ofcommands to cause the memory device to perform the targeted refresh. Inone embodiment, the memory controller is to send an activate refreshcommand followed by a precharge command. In one embodiment, the memorycontroller is to send a targeted refresh command multiple times insequence. In one embodiment, the memory controller is to send adifferent address with each of the targeted refresh commands in thesequence. In one embodiment, the memory device is to generate a sequenceof commands in response to the targeted refresh command from the memorycontroller.

In one aspect a method includes performing: receiving an indication thatrepeated access to a specific row of memory in a memory device exceeds athreshold, identifying an address of the row of memory, and sending acommand to the memory device to perform a targeted refresh, the commandto cause the memory device to perform a refresh targeted to a rowphysically adjacent to the identified row.

In one embodiment, the method includes identifying a specific physicaladdress for the specific row. In one embodiment, the method includesidentifying a virtual address of the specific row that the memory devicemaps to a physical address of the physically adjacent row. In oneembodiment, the method includes identifying an address of the specificrow associated with the indication of repeated access, wherein thememory device identifies the physically adjacent row based on theaddress of the specific row associated with the indication of repeatedmemory access and a configuration of the memory device.

In one embodiment, the method includes identifying a region of memorythat includes the specific row, wherein the memory device refreshes theidentified region, including the physically adjacent row. In oneembodiment, the method includes identifying the address inside thecommand. In one embodiment, the method includes sending the commandembedded in an activation command for the memory device. In oneembodiment, the method includes setting a value in a Mode Register.

In one embodiment, the method includes sending a sequence of commands tocause the memory device to perform the targeted refresh. In oneembodiment, the method includes sending an activate refresh commandfollowed by a precharge command. In one embodiment, the method includessending a targeted refresh command multiple times in sequence. In oneembodiment, the method includes sending a different address with each ofthe targeted refresh commands in the sequence. In one embodiment, themethod includes causing the memory controller to generate a sequence ofcommands in response to the targeted refresh command from the memorycontroller.

Flow diagrams as illustrated herein provide examples of sequences ofvarious process actions. Although shown in a particular sequence ororder, unless otherwise specified, the order of the actions can bemodified. Thus, the illustrated embodiments should be understood only asan example, and the process can be performed in a different order, andsome actions can be performed in parallel. Additionally, one or moreactions can be omitted in various embodiments; thus, not all actions arerequired in every embodiment. Other process flows are possible.

To the extent various operations or functions are described herein, theycan be described or defined as software code, instructions,configuration, and/or data. The content can be directly executable(“object” or “executable” form), source code, or difference code(“delta” or “patch” code). The software content of the embodimentsdescribed herein can be provided via an article of manufacture with thecontent stored thereon, or via a method of operating a communicationinterface to send data via the communication interface. A machinereadable storage medium can cause a machine to perform the functions oroperations described, and includes any mechanism that stores informationin a form accessible by a machine (e.g., computing device, electronicsystem, etc.), such as recordable/non-recordable media (e.g., read onlymemory (ROM), random access memory (RAM), magnetic disk storage media,optical storage media, flash memory devices, etc.). A communicationinterface includes any mechanism that interfaces to any of a hardwired,wireless, optical, etc., medium to communicate to another device, suchas a memory bus interface, a processor bus interface, an Internetconnection, a disk controller, etc. The communication interface can beconfigured by providing configuration parameters and/or sending signalsto prepare the communication interface to provide a data signaldescribing the software content. The communication interface can beaccessed via one or more commands or signals sent to the communicationinterface.

Various components described herein can be a means for performing theoperations or functions described. Each component described hereinincludes software, hardware, or a combination of these. The componentscan be implemented as software modules, hardware modules,special-purpose hardware (e.g., application specific hardware,application specific integrated circuits (ASICs), digital signalprocessors (DSPs), etc.), embedded controllers, hardwired circuitry,etc.

Besides what is described herein, various modifications can be made tothe disclosed embodiments and implementations of the invention withoutdeparting from their scope. Therefore, the illustrations and examplesherein should be construed in an illustrative, and not a restrictivesense. The scope of the invention should be measured solely by referenceto the claims that follow.

What is claimed is:
 1. An apparatus comprising: a detector logic todetermine that a number of activates of a target row of a memory devicewithin a time period meets or exceeds a threshold; and a memorycontroller to cause the memory device to enter a targeted refresh modeand to cause refresh in the targeted refresh mode of only a limitednumber of rows physically proximate to the target row based at least inpart on a determination that the number of activates within the timeperiod meets or exceeds the threshold.
 2. The apparatus of claim 1,wherein the time period comprises a refresh window.
 3. The apparatus ofclaim 1, wherein to cause the memory device to enter the targetedrefresh mode comprises the memory controller to set a mode register ofthe memory device.
 4. The apparatus of claim 1, wherein to cause refreshof the limited number of rows physically proximate to the target rowcomprises the memory controller to provide a target row address withtarget bank group and target bank address to the memory device.
 5. Theapparatus of claim 1, wherein to cause refresh of the limited number ofrows physically proximate to the target row comprises the memorycontroller to send an activate command followed by a precharge command.6. The apparatus of claim 1, wherein to cause refresh of the limitednumber of rows physically proximate to the target row comprises thememory controller to cause the memory device to perform a targetedrefresh based at least in part on the target row address.
 7. Theapparatus of claim 6, wherein the memory device comprising logic toidentify the physically proximate row or region associated with thetarget row address.
 8. The apparatus of claim 6, wherein the memorycontroller is to cause the memory device to determine a physical addressof the physically proximate row based on a logical address of the targetrow.
 9. The apparatus of claim 1, wherein the victim row comprises a rowphysically adjacent to the target row.
 10. The apparatus of claim 1,wherein the memory device includes a dynamic random access memory (DRAM)device compliant with a dual data rate version 4 (DDR4) standard orcompliant with a wide input/output (WIO) memory standard.
 11. Theapparatus of claim 1, wherein the memory controller comprises thedetector logic.
 12. The apparatus of claim 1, wherein the detector logicis to determine a count of the number of activates within the timeperiod of the target row and to indicate when the count meets or exceedsthe threshold.
 13. A system comprising: a memory device including atarget row and a victim row physically proximate to the target row; adetector logic to determine that a number of activates of the target rowwithin a time period meets or exceeds a threshold; and a memorycontroller coupled to the memory device to send one or more commands tocause the memory device to enter a targeted refresh mode and to causerefresh of the victim row based at least in part on a determination thatthe number of activates within the time period meets or exceeds thethreshold, a memory controller to cause the memory device to enter atargeted refresh mode and to cause refresh in the targeted refresh modeof only a limited number of rows physically proximate to the target rowbased at least in part on a determination that the number of activateswithin the time period meets or exceeds the threshold.
 14. The system ofclaim 13, wherein the time period comprises a refresh window.
 15. Thesystem of claim 13, wherein to send one or more commands to cause thememory device to enter the targeted refresh mode comprises the memorycontroller to send a mode register set command to set a mode register ofthe memory device.
 16. The system of claim 13, wherein to send one ormore commands to cause refresh of the victim row comprises the memorycontroller to send a command including a target row address with targetbank group and target bank address to the memory device.
 17. The systemof claim 13, wherein to send one or more commands to cause refresh ofthe victim row comprises the memory controller to send an activatecommand followed by a precharge command.
 18. The system of claim 13,wherein the memory device is further to perform a targeted refresh ofthe victim row based at least in part on the target row address.
 19. Thesystem of claim 18, wherein the memory device further comprises logic toidentify the victim row or region associated with the target rowaddress.
 20. The system of claim 18, wherein the memory device isfurther to determine a physical address of one or more victim rows basedon a logical address of the target row.
 21. The system of claim 13,wherein the memory device comprises the detector logic.
 22. The systemof claim 13, wherein the memory controller comprises the detector logic.23. The system of claim 13, wherein the victim row comprises a rowphysically adjacent to the target row.
 24. The system of claim 13,wherein the memory device includes a dynamic random access memory (DRAM)device compliant with a dual data rate version 4 (DDR4) standard orcompliant with a wide input/output (WIO) memory standard.
 25. The systemof claim 13, wherein the detector logic is to determine a count of thenumber of activates within the time period of the target row and toindicate when the count meets or exceeds the threshold.
 26. The systemof claim 13, further comprising one or more of: at least one processorcommunicatively coupled to the memory controller; a displaycommunicatively coupled to display data from the memory device; abattery to power the system; or a network interface communicativelycoupled to exchange data stored in the memory device with a remotedevice over a network connection.
 27. A method comprising: determiningthat a number of activates of a target row of a memory device within atime period meets or exceeds a threshold; triggering the memory deviceto enter a targeted refresh mode; and sending one or more commands tocause the memory device to refresh in the targeted refresh mode only alimited number of rows physically proximate to the target row based atleast in part on determining that the number of activates within thetime period meets or exceeds the threshold.
 28. The method of claim 27,wherein the time period comprises a refresh window.
 29. The method ofclaim 27, wherein triggering the memory device to enter the targetedrefresh mode comprises setting a mode register of the memory device. 30.The method of claim 27, wherein sending one or more commands to causethe memory device to refresh the limited number of rows physicallyproximate to the target row comprises sending an activate commandfollowed by a precharge command.
 31. The method of claim 27, whereinsending one or more commands to cause the memory device to refresh thelimited number of rows physically proximate to the target row furthercomprises providing an address of the target row with target bank groupand target bank address.
 32. The method of claim 31, wherein sending oneor more commands to cause the memory device to refresh the limitednumber of rows physically proximate to the target row comprises sendingthe one or more commands to cause the memory device to identify the atleast one row physically proximate to the target row based on the targetrow address.
 33. The method of claim 31, wherein sending one or morecommands to cause the memory device to refresh the limited number ofrows physically proximate to the target row comprises sending the one ormore commands to cause the memory device to identify the at least onerow physically proximate to the target row based on a logical address ofthe target row.
 34. The method of claim 27, wherein refreshing thevictim row comprises refreshing one or more rows physically adjacent tothe target row.
 35. The method of claim 27, wherein the memory deviceincludes a dynamic random access memory (DRAM) device compliant with adual data rate version 4 (DDR4) standard or compliant with a wideinput/output (WIO) memory standard.
 36. The method of claim 27, whereindetermining that the number of activates within the time period meets orexceeds the threshold comprises the memory device making adetermination.
 37. The method of claim 27, wherein determining that thenumber of activates within the time period meets or exceeds thethreshold comprises the memory controller making a determination. 38.The method of claim 27, wherein determining that the number of activateswithin the time period meets or exceeds the threshold comprises countingthe number of activates within the time period.
 39. An apparatuscomprising: means for determining that a number of activates of a targetrow of a memory device within a time period meets or exceeds athreshold; means for triggering the memory device to enter a targetedrefresh mode; and means for sending one or more commands to cause thememory device to refresh in the targeted refresh mode only a limitednumber of rows physically proximate to the target row based at least inpart on determining that the number of activates within the time periodmeets or exceeds the threshold.
 40. The apparatus of claim 39, whereinthe time period comprises a refresh window.
 41. The apparatus of claim39, wherein the means for triggering the memory device to enter thetargeted refresh mode comprises means for setting a mode register of thememory device.
 42. The apparatus of claim 39, wherein the means forsending one or more commands to cause the memory device to refresh thelimited number of rows physically proximate to the target row comprisesmeans for sending an activate command followed by a precharge command.43. The apparatus of claim 39, wherein the means for sending one or morecommands to cause the memory device to refresh the limited number ofrows physically proximate to the target row comprises means for sendingthe one or more commands to cause the memory device to identify the atleast one row physically proximate to the target row based on the targetrow address.
 44. The apparatus of claim 39, wherein the means forrefreshing the victim row comprises means for refreshing one or morerows physically adjacent to the target row.
 45. The apparatus of claim39, wherein the memory device includes a dynamic random access memory(DRAM) device compliant with a dual data rate version 4 (DDR4) standardor compliant with a wide input/output (WIO) memory standard.
 46. Theapparatus of claim 39, further comprising means for determining that thenumber of activates within the time period meets or exceeds thethreshold including means for counting the number of activates withinthe time period.